The present invention relates to a multi-gap spark ignition device to be installed in a spark-ignition engine.
Recently, lean-burn system, exhaust gas recirculation system or the like has been adopted in order to reduce harmful components in the exhaust gases of an automobile and in order to prevent the waste of resources. In these systems, excellent ignitability and high combustion speed are required.
The ignitability and the combustion speed can be improved by increasing the number of igniters so as to promote the flame transmission within a combustion chamber. However, in this case, the number of igniters and distributers must be increased.
In order to reduce the number of the igniters and the distributers, such a system that a plurality of spark gaps are formed in series, has been proposed.
FIGS. 1, 2 illustrate a conventional multi-gap spark ignition device, respectively.
A base member 4 formed of an electrically insulating ceramic plate, is mounted between a cylinder head 5 and a cylinder block 6 of an internal combustion engine of an automobile while sandwiching a gasket 7 between the base member 4 and the cylinder head 5, and between the base member 4 and the cylinder block 6, respectively.
A hole 40 is formed in the base member 4 so as to form one portion of the combustion chamber 8.
A high voltage electrode 1, an earth electrode 2, and a plurality of intermediate electrodes 3A, 3B, 3C, 3D and 3E which are arranged at regular intervals between the high voltage electrode 1 and the contact electrode 2, are embedded within the opposed walls of the base member 4 defining the hole 40 as to project into the hole 40. And a plurality of spark gaps are formed between the adjacent electrodes in series.
However, the ceramic base member 4 is liable to be broken while being assembled or due to thermal strain occuring when the internal combustion engine operates.
In another conventional multi-spark gap ignition device, a plurality of plugs each of which is formed by covering the high voltage electrodes and the intermediate electrode with the electrically insulating material, are screwed into the wall defining the combustion chamber, by means of bolts so as to penetrate therethrough.
However, in this device, excellent workability cannot be obtained.
Particularly, in the multi-cylinder type engine, a large number of plugs for adjacent cylinders must be fixed to the same wall portion of the base member so that the interference between adjacent electrodes is liable to occur.
On the other hand, a multi-gap spark ignition device wherein a plurality of spark gaps are formed in series also has a problem that as the number of spark gaps increase, the required voltage increases so that the electric power consumption increases.
One object of the present invention is to provide a multi-gap spark ignition device for an engine, having a simple construction, wherein a plurality of electrodes are easily mounted on a base member.
Another object of the present invention is to provide a durable multi-gap spark ignition device of which the base member is not broken.
Still another object of the present invention is to provide a multi-gap spark ignition device of which the required voltage for generating spark in each gap is low as compared with the conventional ignition device.